Enlarge ImageConundrum. Researchers can't predict why methane (red and yellow areas) is so spotty in the Martian atmosphere. Credit: NASA Just as researchers were once again getting their hopes up, a new study undercuts the prospects for martian life. Scientists have discovered that methane in the martian atmosphere, one of the primary signals that biological processes may be at work today on the red planet, is behaving in unexplainable ways. The results challenge the latest evidence suggesting that Mars is--or was ever--inhabited. Mars has been a roller coaster for astrobiologists. In 1996, for example, researchers reported that a martian...